Dipyridamole thallium-201 scintigraphy for early risk stratification of patients after uncomplicated myocardial infarction

Abstract

Objective: To determine the safety and prognostic value of dipyridamole thallium-201 scintigraphy performed in patients within three to five days of acute myocardial infarction, including those receiving thrombolytic treatment.

Design: A prospective study of dipyridamole thallium-201 scintigraphy in patients early after acute myocardial infarction.

Setting: University hospital.

Patients: 200 patients who were clinically uncomplicated at day 3 after infarction, 92 (46%) of whom had received thrombolysis.

Main outcome measures: Incidence of cardiac death, non-fatal reinfarction, readmission to hospital for unstable angina, or non-elective revascularisation procedure within six months' follow up.

Results: No patient had a serious complication from the dipyridamole study. At six month follow up, 55 patients (28%) had suffered a defined cardiac event. Patients who received thrombolysis had the same extent of thallium-201 redistribution and the same occurrence of subsequent cardiac events as those not receiving thrombolysis. Patients who subsequently had an event had more myocardial segments showing thallium-201 redistribution than event free patients: 2.7 (SD 1.9) v 1.2 (1.4), respectively (p < 0.001). Among all clinical and scintigraphic variables, multivariate analysis identified the extent of thallium-201 redistribution as the only independent predictor of outcome (p < 0.001). Among 63 patients (32%) of the study cohort who showed more than two myocardial segments with thallium-201 redistribution, the adjusted risk ratio for a cardiac event was 7.5 (95% confidence interval 2.9 to 19.1) compared with patients without any redistribution.

Conclusions: Dipyridamole thallium-201 scintigraphy can be performed safely within a few days of the event in patients with uncomplicated myocardial infarction, including those who received thrombolysis, and can identify a subgroup of patients at high risk of future ischaemic events.

Figure 1

Schematic diagram showing myocardial thallium profiles in the 35° left anterior oblique, anterior, and 75° left anterior oblique projections. The individual myocardial segments in each projection and the scoring of thallium activity in each myocardial segment are also shown. LAO, left anterior oblique.